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Mesa Will Not Support GL_ARB_compatibility

08-31-2012, 12:50 PM

Phoronix: Mesa Will Not Support GL_ARB_compatibility

Intel OTC developers that generally have been providing most of the new OpenGL functionality within Mesa have shared their views this week that they will not be implementing the GL_ARB_compatibility extension within the open-source project...

Comment

I'm a bit confused on this, actually. Is this extension only used when creating a GL 3.1+ GL contexts where you also want to use old GL features that have been removed?

As a related question, will Mesa offer the ability to create either a GL 2.x (or 3.0) context with the legacy features or a 3.1+ context without the old stuff when requested? If so, I don't see much issue... Legacy games can use the GL 2.1/3.0 codepaths, and 3.1+ games can use the new stuff without the legacy features. It's just in the interim, where we have games that expect 3.1+ and compatibility features that we'll have issues. And hopefully there won't be too many of those.

As a related question, will Mesa offer the ability to create either a GL 2.x (or 3.0) context with the legacy features or a 3.1+ context without the old stuff when requested? If so, I don't see much issue... Legacy games can use the GL 2.1/3.0 codepaths, and 3.1+ games can use the new stuff without the legacy features. It's just in the interim, where we have games that expect 3.1+ and compatibility features that we'll have issues. And hopefully there won't be too many of those.

The problem is that compatibility contexts do get used (from an application developer standpoint, there's not much reason to use the core context with less features), and application developers usually don't target Mesa, but rather the proprietary Nvidia and AMD drivers, which do support GL_ARB_compatibility.

That said, though, Apple support GL 3.2 core contexts but not compatibility contexts, so games targeting OS X and using new OpenGL features will already be using core contexts.

Comment

As a related question, will Mesa offer the ability to create either a GL 2.x (or 3.0) context with the legacy features or a 3.1+ context without the old stuff when requested?\

Yes. We will continue to support OpenGL 3.0 as the default context mode. When a application specifically requests a 3.1 context, it will get 3.1 without the old stuff. When we support 3.2 (and later), we will only support the core profile.

Comment

Yes. We will continue to support OpenGL 3.0 as the default context mode. When a application specifically requests a 3.1 context, it will get 3.1 without the old stuff. When we support 3.2 (and later), we will only support the core profile.

MacOS X works the same way, except Mac don't support 3.0 at all. The default on Mac is a 2.1 context, but an application can request a 3.1 or 3.2 context without the old stuff. OpenGL 3.3 and 4.x are not yet supported on Mac either.